Re: Re: Radicals simplify

*To*: mathgroup at smc.vnet.net*Subject*: [mg106409] Re: [mg106378] Re: [mg106361] Radicals simplify*From*: "David Park" <djmpark at comcast.net>*Date*: Mon, 11 Jan 2010 18:53:52 -0500 (EST)*References*: <201001100830.DAA05621@smc.vnet.net> <31173649.1263207631979.JavaMail.root@n11>

This can be simplified to the posters desired expression with Presentations. Needs["Presentations`Master`"] (x^6*y^3)^(1/4) MapAt[FactorOut[x^2, Identity, CreateSubexpression], %, 1] Simplify[%, x >= 0] // ReleaseSubexpressions[] (x^6 y^3)^(1/4) (x^4 y^3 (x^2))^(1/4) x (x^2 y^3)^(1/4) We factored x^2 out of the product and protected it by making it a Subexpression. Then used Simplify and released the Subexpression. David Park djmpark at comcast.net http://home.comcast.net/~djmpark/ From: Andrzej Kozlowski [mailto:akoz at mimuw.edu.pl] On 10 Jan 2010, at 17:30, francix wrote: > Hi, > I am using Matematica 7 and need some help with Radicals. > > If I do > Simplify[(x^4 y^3)^(1/4), x >= 0] I correctly have > > x (y^3)^(1/4) > > But If I do > > Simplify[(x^6 y^3)^(1/4), x >= 0] I get > > (x^6 y^3)^(1/4) and not the correct answer x(x^2 y^3)^(1/4) > > Thanks in advanced. > The problem is that your desired formula has a higher ComplexityFunction than the one returned by Mathematica. Mathematica's default ComplexityFunction is close to LeafCount and LeafCount[x*(x^2*y^3)^(1/4)] 13 while LeafCount[(x^6*y^3)^(1/4)] 11 The quickest way to get the answer close to the one you want in this case is: Refine[(x^6*y^3)^(1/4), x >= 0] x^(3/2)*(y^3)^(1/4) To get exactly the answer you want you will need to play with ComplexityFunction, which in this case will be tricky. Andrzej Kozlowski

**References**:**Radicals simplify***From:*"francix" <fracix@gmail.com>